Client crash when joining server - Ticking Screen - Map Writer config error

This crash has been observed on Yogscast Complete but is not limited to that modpack

Symptoms

When joining a server the client crashes. The start of the crash report looks similar to this:

---- Minecraft Crash Report ----
// Hey, that tickles! Hehehe!

Time: 9/21/14 4:44 PM
Description: Ticking screen

java.lang.RuntimeException: Unknown character ' ' in '/saves/mapwriter_mp_worlds/SERVER_IP_PORT/mapwriter.cfg:1'
at net.minecraftforge.common.Configuration.load(Configuration.java:625)
at net.minecraftforge.common.Configuration.(Configuration.java:100)
at net.minecraftforge.common.Configuration.(Configuration.java:106)

Where SERVER_IP_PORT is the address of the server that you are connecting to in the format 127_0_0_1_25565

Cause

The crash is caused when the Forge config loader is called by the Map Writer mod to load the Map Writer config for the server you are joining. The first line contains an invalid character (likely an extra space where there shouldn't be) and the config loader crashes.

Somwhow the config file was malformed when it was created and the config loader is unable to handle a malformed config file.

Solutions

These solutions assume you are running Yogscast Complete from the AT Launcher.

A: Locate and delete the file:

• Open AT Launcher
• Go to 'Instances'
• Find your instance of Yogscast Complete
• Click 'Open Folder'
• Browse to /saves/mapwriter_mp_worlds/69_162_66_20_25815/
• Delete the file 'mapwriter.cfg'
• The file will be re-crated when you join the server again, hopefully correctly this time

B: Locate and edit the file:

• Open AT Launcher
• Go to 'Instances'
• Find your instance of Yogscast Complete
• Click 'Open Folder'
• Browse to /saves/mapwriter_mp_worlds/69_162_66_20_25815/
• Edit the file 'mapwriter.cfg', find the extra space character on the first line and delete it

C: Disable the Map Writer mod

• Map Writer is not required to connect tot he server, you can safely disable it
• Open AT Launcher
• Go to 'Instances'
• Find your instance of Yogscast Complete
• Click 'Edit Mods'
• Find 'Map Writer'in the left column and tick the box next to it
• Click 'Disable Mod'
• Click 'Close'
• Your client will now start without the mod